Lichens of the National Forests in Alaska United States Forest Service R10-RG-170 Department of Alaska Region August 2006 Agriculture What is a Lichen? You can think of lichens as fungi that have discovered farm- ing. Instead of parasitizing or scavenging other organisms for a living (such as molds, mildews, mushrooms), lichen fungi cultivate tiny algae and/or blue-green bacteria (called cyanobacteria) within the fabric of interwoven fungal threads that form the lichen body (or thallus). The algae and cyano- bacteria produce food for the fungus by converting the sun’s energy into sugars through photosynthesis. Perhaps the most important contribution of the fungus is to provide a protective habitat for the algae or cyanobacteria. Thus, lichens are a combination of two or three organisms that live together inti- mately. The green or blue-green photosynthetic layer is often visible between two white fungal layers if a piece of lichen thallus is torn off. In some cases, the fungus and the photosynthetic partner that together make the lichen may be found living separately in nature. However, many lichen-forming fungi cannot exist by themselves because they have become dependent on their photosynthetic partners for survival. But in all cases, a fungus looks quite different in the lichenized form compared to its free-living form. How do Lichens Reproduce? Lichens sexually reproduce with fruiting bodies of various colors that can look like miniature mushrooms. These are called apothecia (Fig. 1) and contain spores that germinate and grow into the fungus. This fungus must find the right photosynthetic partner in order to become a lichen. Lichens reproduce asexually in several ways. Some lichens have openings on the thallus Figure 1. Apothecia, fruiting surface called soralia (Fig. 2). bodies. Inside, tiny dust-like granules called soredia (Fig. 3) are Figure 2. Soralia, small Figure 3. Soredia, dust-like openings on thallus surface. granules. 2 Figure 5. Lobules, flaps of tissue. Figure 4. Isidia, tiny projections. produced. Soredia contain algae and fungal cells that escape from the parent lichen and grow into a new lichen thallus. Other lichens produce outgrowths that break off and grow into the same lichen they came from. These are called isidia (tiny, cylindrical projections, Fig. 4) or lobules (little flaps of tissue, Fig. 5). These structures are often very important for the proper identification of lichens. Diversity and Ecology Lichens come in many shapes, sizes, and colors. A lichen thallus has one of three general growth forms: foliose, fruti- cose, or crustose. Foliose lichens are leaf-like with different upper and lower surfaces. Fruticose lichens are hair-like or bushy with no obvious difference between upper and lower surfaces. Crustose lichens are so closely attached to a surface, like paint spots, that the lower surface is not easily observable. Lichens have specialized features enabling them to survive long periods of drought. In a dehydrated, inactive state they can resist extreme high and low temperatures and still function optimally whenever conditions become just right. Well adapted for life in marginal habitats, lichens produce more than 500 unique biochemical compounds that serve to control light exposure, repel herbivores and microbes, and discourage competition from plants. Among these are many pigments and antibiotics that are useful to humans. Lichens are considered to be nature’s pioneers because they colonize newly exposed surfaces. Lichens containing cyanobacteria fix their own nitrogen from the air into a form usable by other plants. This form of nitrogen is released into the environment as rain washes the lichens or when lichens die and fall to the ground. These lichen types tend to live in nitrogen-poor habitats such as bare rock surfaces, the forest canopy, or on sandy soils. 3 Lichens provide food for many animals including flying squir- rels, black-tailed deer, and mountain goats. Many inverte- brates use lichens for food or for shelter. The national forests in Alaska contain a myriad of habitats where more than 500 species of lichens thrive. A few lichens are generalists and can be found across many different habi- tats, while most are very habitat specific. Lichens and Air Quality Monitoring Lichens are not protected by bark, nor do they possess an external waxy layer to prevent water loss like plant leaves. Lacking roots and other structures to transport food and water, lichens absorb moisture into the thallus directly from the humid air or rainfall, and can become quickly saturated like a sponge. Lichens dry out by continually losing moisture through evaporation when windy or dry conditions exist. As drying occurs, elements and compounds that entered with moisture from the surrounding environment become concentrated in the lichen. During high rainfall periods, mobile nutrients and pollutants are leached from a lichen. In this way lichens serve as dynamically representative samples of the environmental conditions in which they are growing. Lichen species differ in their tolerance to air pollutants, with responses ranging from relatively resistant to highly sensi- tive. Measurements of metals, nitrogen, and sulfur content in lichens at different locations indicate the relative amounts of pollution in the air. The Forest Service uses lichens to moni- tor air quality on both national forests in the Alaska Region, primarily in wilderness areas. Lichens used for air quality monitoring in the Alaska Region are noted in this brochure. The lichens featured in this brochure are arranged by the three general growth forms described above: foliose, fruti- cose, and crustose. 4 Foliose Beaded tube lichen Hypogymnia apinnata Thallus made up of tube-like lobes, constricted at intervals, usually has a hole at the tip of each lobe; white upper surface and black underneath. Apothecia raised and brown. Occurs in forests of all types (conifers and hardwoods), but not in deep shade. Used in air quality monitoring. Thirteen species of Hypogymnia occur in the Alaska Region. Gray lungwort Lobaria halli Large leaf-like thallus, light gray when dry, dark gray when wet. Soralia brown to gray and sometimes ring-like on upper surface. Contains cyanobacte- ria. Found in Sitka spruce and hardwood forests, but more common on sites with cot- tonwood, birch, and alder. Nine species of Lobaria occur in the Alaska Region. Cabbage lungwort Lobaria linita Large leaf-like thallus, green or brownish-green when dry, bright grass-green when wet. Often with abundant, orange apothecia on upper surface. Contains cyanobacteria. Used as winter forage by mountain goats. It grows in shady conifer- ous forests on lower trunks. 5 Foliose Lettuce lichen Lobaria oregana Large leaf-like thallus; pale yellowish-green on top, white and tan on the bottom. Lobe margins decorated with tiny, flat lobules. Contains cyano- bacteria. Occurs in the canopy of old-growth forests and along forest edges. Also grows on hardwood trees. Used in air quality monitoring. Lungwort Lobaria pulmonaria Large leaf-like thallus; pale brown to olive brown when dry, bright green when wet. Strongly pitted upper surface with soralia on lobe margins. Contains cyanobacteria. Occurs in riparian Sitka spruce forests, hardwood forests, and maritime beach forests. Arctic kidney lichen Nephroma arcticum Large thallus; yellowish-green when dry, bright green when wet. Broad, flat, gray bumps on surface that contain cyanobac- teria. Lower surface pale tan at the edge. Large orange-brown apothecia. In coniferous forests and occasionally on the forest floor or old logs. Nine species of Nephroma occur in the Alaska Region. 6 Foliose Pimpled kidney lichen Nephroma resupinatum Medium-sized thallus; upper surface brown to grayish brown, lobe tips with woolly appear- ance. Lower surface pale, fuzzy with scattered whitish bumps. Contains cyanobacteria. In hu- mid forests on hardwoods and conifers. Salted shield lichen Parmelia saxatilis Small thallus of tiny flattened lobes; 2–4 mm wide, pale green to gray. Upper surface with small net-like ridges and isidia, underside with black rhizines (small stiff hairs). Apothecia brown. In exposed and shaded habitats including coniferous and hardwood forests, and on rocks in upper tidal and alpine areas. Seven species of Parmelia occur in the Alaska Region. Flaky freckle pelt Peltigera britannica Large thallus; brownish-green when dry, grass green when wet. Underside has raised veins with tiny rhizines. Lobes have small granules that rub off easily and contain cyanobacteria. In humid forests on tree trunks, branches, and mossy soil. Twenty-two species of Peltigera occur in the Alaska Region. 7 Foliose Tree pelt lichen Peltigera collina Medium-sized thallus; gray to dark brown. Upper surface smooth with bluish gray soredia usually covering lobe margins; lower surface pale with small raised veins and tufted rhizines. Contains cyanobacteria. In humid forests on conifers and hardwoods. Varied rag lichen Platismatia glauca Medium-sized thallus; pale greenish-gray, often brown at the edges. Lobe margins very frilly with soredia and isidia. Lower surface shiny and brown with white patches. In the canopy of coniferous forests and on hardwoods. Used in air quality monitoring. Four spe- cies of Platismatia occur in the Alaska Region. Crinkled rag lichen Platismatia lacunosa Medium-sized thallus; pale green to almost white. Upper surface deeply pitted and ridged. In coniferous forest canopy and on hardwoods. Foliose Dimpled specklebelly lichen Pseudocyphellaria anomala Medium to large thallus; chocolate to reddish brown. Upper surface with a net- work of ridges and dimples; ridges set off by white and gray soredia. Lower surface with conspicuous raised, white dots. In humid forests on conifers and hardwoods. Five species of Pseudocyphellaria occur in the Alaska Region. Orange chocolate chip lichen Solarina crocea Medium-sized thallus; olive- brown to olive-gray on upper surface, lower surface bright orange with veins and scattered rhizines. Apothecia are brown and sunk into upper surface. Contains cyanobacteria. On soils in moist areas under late snow patches or seepage areas in cold, open habitats.